// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/runtime-profiler.h"

#include "src/assembler.h"
#include "src/base/platform/platform.h"
#include "src/bootstrapper.h"
#include "src/compilation-cache.h"
#include "src/compiler.h"
#include "src/execution.h"
#include "src/frames-inl.h"
#include "src/global-handles.h"
#include "src/interpreter/interpreter.h"
#include "src/tracing/trace-event.h"

namespace v8 {
namespace internal {

    // Number of times a function has to be seen on the stack before it is
    // optimized.
    static const int kProfilerTicksBeforeOptimization = 2;

    // The number of ticks required for optimizing a function increases with
    // the size of the bytecode. This is in addition to the
    // kProfilerTicksBeforeOptimization required for any function.
    static const int kBytecodeSizeAllowancePerTick = 1200;

    // Maximum size in bytes of generate code for a function to allow OSR.
    static const int kOSRBytecodeSizeAllowanceBase = 180;

    static const int kOSRBytecodeSizeAllowancePerTick = 48;

    // Maximum size in bytes of generated code for a function to be optimized
    // the very first time it is seen on the stack.
    static const int kMaxBytecodeSizeForEarlyOpt = 90;

#define OPTIMIZATION_REASON_LIST(V)     \
    V(DoNotOptimize, "do not optimize") \
    V(HotAndStable, "hot and stable")   \
    V(SmallFunction, "small function")

    enum class OptimizationReason : uint8_t {
#define OPTIMIZATION_REASON_CONSTANTS(Constant, message) k##Constant,
        OPTIMIZATION_REASON_LIST(OPTIMIZATION_REASON_CONSTANTS)
#undef OPTIMIZATION_REASON_CONSTANTS
    };

    char const* OptimizationReasonToString(OptimizationReason reason)
    {
        static char const* reasons[] = {
#define OPTIMIZATION_REASON_TEXTS(Constant, message) message,
            OPTIMIZATION_REASON_LIST(OPTIMIZATION_REASON_TEXTS)
#undef OPTIMIZATION_REASON_TEXTS
        };
        size_t const index = static_cast<size_t>(reason);
        DCHECK_LT(index, arraysize(reasons));
        return reasons[index];
    }

    std::ostream& operator<<(std::ostream& os, OptimizationReason reason)
    {
        return os << OptimizationReasonToString(reason);
    }

    RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
        : isolate_(isolate)
        , any_ic_changed_(false)
    {
    }

    static void TraceRecompile(JSFunction function, const char* reason,
        const char* type)
    {
        if (FLAG_trace_opt) {
            PrintF("[marking ");
            function->ShortPrint();
            PrintF(" for %s recompilation, reason: %s", type, reason);
            PrintF("]\n");
        }
    }

    void RuntimeProfiler::Optimize(JSFunction function, OptimizationReason reason)
    {
        DCHECK_NE(reason, OptimizationReason::kDoNotOptimize);
        TraceRecompile(function, OptimizationReasonToString(reason), "optimized");
        function->MarkForOptimization(ConcurrencyMode::kConcurrent);
    }

    void RuntimeProfiler::AttemptOnStackReplacement(InterpretedFrame* frame,
        int loop_nesting_levels)
    {
        JSFunction function = frame->function();
        SharedFunctionInfo shared = function->shared();
        if (!FLAG_use_osr || !shared->IsUserJavaScript()) {
            return;
        }

        // If the code is not optimizable, don't try OSR.
        if (shared->optimization_disabled())
            return;

        // We're using on-stack replacement: Store new loop nesting level in
        // BytecodeArray header so that certain back edges in any interpreter frame
        // for this bytecode will trigger on-stack replacement for that frame.
        if (FLAG_trace_osr) {
            PrintF("[OSR - arming back edges in ");
            function->PrintName();
            PrintF("]\n");
        }

        DCHECK_EQ(StackFrame::INTERPRETED, frame->type());
        int level = frame->GetBytecodeArray()->osr_loop_nesting_level();
        frame->GetBytecodeArray()->set_osr_loop_nesting_level(
            Min(level + loop_nesting_levels, AbstractCode::kMaxLoopNestingMarker));
    }

    void RuntimeProfiler::MaybeOptimize(JSFunction function,
        InterpretedFrame* frame)
    {
        if (function->IsInOptimizationQueue()) {
            if (FLAG_trace_opt_verbose) {
                PrintF("[function ");
                function->PrintName();
                PrintF(" is already in optimization queue]\n");
            }
            return;
        }

        if (FLAG_always_osr) {
            AttemptOnStackReplacement(frame, AbstractCode::kMaxLoopNestingMarker);
            // Fall through and do a normal optimized compile as well.
        } else if (MaybeOSR(function, frame)) {
            return;
        }

        if (function->shared()->optimization_disabled())
            return;

        OptimizationReason reason = ShouldOptimize(function, function->shared()->GetBytecodeArray());

        if (reason != OptimizationReason::kDoNotOptimize) {
            Optimize(function, reason);
        }
    }

    bool RuntimeProfiler::MaybeOSR(JSFunction function, InterpretedFrame* frame)
    {
        int ticks = function->feedback_vector()->profiler_ticks();
        // TODO(rmcilroy): Also ensure we only OSR top-level code if it is smaller
        // than kMaxToplevelSourceSize.

        if (function->IsMarkedForOptimization() || function->IsMarkedForConcurrentOptimization() || function->HasOptimizedCode()) {
            // Attempt OSR if we are still running interpreted code even though the
            // the function has long been marked or even already been optimized.
            int64_t allowance = kOSRBytecodeSizeAllowanceBase + static_cast<int64_t>(ticks) * kOSRBytecodeSizeAllowancePerTick;
            if (function->shared()->GetBytecodeArray()->length() <= allowance) {
                AttemptOnStackReplacement(frame);
            }
            return true;
        }
        return false;
    }

    OptimizationReason RuntimeProfiler::ShouldOptimize(JSFunction function,
        BytecodeArray bytecode)
    {
        int ticks = function->feedback_vector()->profiler_ticks();
        int ticks_for_optimization = kProfilerTicksBeforeOptimization + (bytecode->length() / kBytecodeSizeAllowancePerTick);
        if (ticks >= ticks_for_optimization) {
            return OptimizationReason::kHotAndStable;
        } else if (!any_ic_changed_ && bytecode->length() < kMaxBytecodeSizeForEarlyOpt) {
            // If no IC was patched since the last tick and this function is very
            // small, optimistically optimize it now.
            return OptimizationReason::kSmallFunction;
        } else if (FLAG_trace_opt_verbose) {
            PrintF("[not yet optimizing ");
            function->PrintName();
            PrintF(", not enough ticks: %d/%d and ", ticks,
                kProfilerTicksBeforeOptimization);
            if (any_ic_changed_) {
                PrintF("ICs changed]\n");
            } else {
                PrintF(" too large for small function optimization: %d/%d]\n",
                    bytecode->length(), kMaxBytecodeSizeForEarlyOpt);
            }
        }
        return OptimizationReason::kDoNotOptimize;
    }

    void RuntimeProfiler::MarkCandidatesForOptimization()
    {
        HandleScope scope(isolate_);

        if (!isolate_->use_optimizer())
            return;

        DisallowHeapAllocation no_gc;
        TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.compile"),
            "V8.MarkCandidatesForOptimization");

        // Run through the JavaScript frames and collect them. If we already
        // have a sample of the function, we mark it for optimizations
        // (eagerly or lazily).
        int frame_count = 0;
        int frame_count_limit = FLAG_frame_count;
        for (JavaScriptFrameIterator it(isolate_);
             frame_count++ < frame_count_limit && !it.done();
             it.Advance()) {
            JavaScriptFrame* frame = it.frame();
            if (!frame->is_interpreted())
                continue;

            JSFunction function = frame->function();
            DCHECK(function->shared()->is_compiled());
            if (!function->shared()->IsInterpreted())
                continue;

            if (!function->has_feedback_vector())
                continue;

            MaybeOptimize(function, InterpretedFrame::cast(frame));

            // TODO(leszeks): Move this increment to before the maybe optimize checks,
            // and update the tests to assume the increment has already happened.
            int ticks = function->feedback_vector()->profiler_ticks();
            if (ticks < Smi::kMaxValue) {
                function->feedback_vector()->set_profiler_ticks(ticks + 1);
            }
        }
        any_ic_changed_ = false;
    }

} // namespace internal
} // namespace v8
